Abstract
Nonalcoholic fatty liver disease (NAFLD) is the leading cause of advanced liver diseases. Fat accumulation in the liver changes the hepatic microstructure and the corresponding statistics of ultrasound backscattered signals. Acoustic structure quantification (ASQ) is a typical model-based method for analyzing backscattered statistics. Shannon entropy, initially proposed in information theory, has been demonstrated as a more flexible solution for imaging and describing backscattered statistics without considering data distribution. NAFLD is a hepatic manifestation of metabolic syndrome (MetS). Therefore, we investigated the association between ultrasound entropy imaging of NAFLD and MetS for comparison with that obtained from ASQ. A total of 394 participants were recruited to undergo physical examinations and blood tests to diagnose MetS. Then, abdominal ultrasound screening of the liver was performed to calculate the ultrasonographic fatty liver indicator (US-FLI) as a measure of NAFLD severity. The ASQ analysis and ultrasound entropy parametric imaging were further constructed using the raw image data to calculate the focal disturbance (FD) ratio and entropy value, respectively. Tertiles were used to split the data of the FD ratio and entropy into three groups for statistical analysis. The correlation coefficient r, probability value p, and odds ratio (OR) were calculated. With an increase in the US-FLI, the entropy value increased (r = 0.713; p < 0.0001) and the FD ratio decreased (r = –0.630; p < 0.0001). In addition, the entropy value and FD ratio correlated with metabolic indices (p < 0.0001). After adjustment for confounding factors, entropy imaging (OR = 7.91, 95% confidence interval (CI): 0.96–65.18 for the second tertile; OR = 20.47, 95% CI: 2.48–168.67 for the third tertile; p = 0.0021) still provided a more significant link to the risk of MetS than did the FD ratio obtained from ASQ (OR = 0.55, 95% CI: 0.27–1.14 for the second tertile; OR = 0.42, 95% CI: 0.15–1.17 for the third tertile; p = 0.13). Thus, ultrasound entropy imaging can provide information on hepatic steatosis. In particular, ultrasound entropy imaging can describe the risk of MetS for individuals with NAFLD and is superior to the conventional ASQ technique.
Highlights
Nonalcoholic fatty liver disease (NAFLD) is characterized by excess and abnormal intracellular accumulation of triglycerides in hepatocytes
To observe how the statistical properties of backscattered signal varied with the severity of NAFLD, dot and box plots of the focal disturbance (FD) ratio and entropy value corresponding to each ultrasonographic fatty liver indicator (US-FLI) were plotted (Figure 2)
Our results showed that both the FD ratio obtained from Acoustic structure quantification (ASQ) analysis and the entropy value of ultrasound entropy imaging correlated with the US-FLI, indicating that these two parameters vary with the progress of NAFLD because macrovesicular steatosis is the major pathological change of NAFLD
Summary
Nonalcoholic fatty liver disease (NAFLD) is characterized by excess and abnormal intracellular accumulation of triglycerides in hepatocytes. Liver biopsy is the gold standard for diagnosing NAFLD [5]. Most patients with NAFLD have no significant clinical symptoms, and performing liver biopsies on such patients is ethically controversial. To resolve this dilemma, noninvasive imaging modalities such as ultrasound, computed tomography, magnetic resonance imaging, and magnetic resonance spectroscopy (MRS) are commonly used for the assessment of hepatic steatosis [8]. Ultrasound imaging provides several advantages, including ease of routine examination, cost-effectiveness, portability, and nonionizing imaging principles, and it is currently the first-line modality for assessing hepatic steatosis and evaluating NAFLD
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